Process for depositing brasslike coatings and composition therefor



United States Patent U.S. Cl. 1061 Claims ABSTRACT OF THE DISCLOSURE Animmersion process and a composition for applying a brasslike finish tosteel by immersing steel in a bath comprising copper, nickel, and tin,together with a complexing agent of the group of boric acid and citricacid, and an enhancing agent of the group of glutaric acid, succinicacid, glycolic acid, their anhydrides, and their water soluble salts.

This invention relates to immersion electrolytic plating, and moreparticularly to electrolytes therefor.

An important object of the invention is to provide plating electrolytesfor use in plating brasslike coatings on objects, which coatings .aresubstantially similar in appearance to those generally known as liquorfinish, and employing a tertiary system of cupric, nickelous andstannous salts.

Another important object of the invention is to provide new and usefulimmersion electrolytic plating electrolytes containing new additions,functioning as complexing and chelating agents for the plating of ametal or metals.

Still another important object of the invention is to provide a new anduseful immersion electroplating electrolyte, containing enhancing andmodifying agents for the complexing and chelating agents.

The added agents improve the thickness, density, adhesion, appearanceand anti-tarnishing characteristics of the plated objects.

In addition, an important object of the invention is to provideimmersion electrolytic plating electrolytes which tend to slow thebuild-up of iron salts in the electrolytes, whereby the useful lives ofthe electrolytes are lengthened.

Another important object of the invention is to provide new and usefulimmersion electrolytic plating electrolytes which contain low tomoderate cost compounds which are readily obtainable and which may beincorporated in a sulfuric acid-containing electrolyte by conventionalsteps, whereby the electrolytes may be produced and marketed at moderateprices.

An additional object of the invention is to provide several chemicalclasses of brightening agents which function in these electrolytes toenhance, improve, and brighten the coating obtained.

Other objects and advantages of the invention will be apparent duringthe course of the following detailed description of the invention.

A preferred example of my complexing and chelating agents is boric acid,and preferred examples of my enhancing and modifying agents are glutaricanhydride, sodium glycolate and succinic anhydride. Examples ofbrightening agents include 3-amino-lH-1, 2,4-triazole and Z-butyne-l,4-diol. Examples of the plating salts are "ice those of copper, nickeland tin, either employed together, any two, or separately. An example ofthe objects to be placed are iron or steel wires or rods.

Numerous classes of chemical compounds have been found to enhance,improve, and brighten the deposited coating. Among these are: magnesiumsalts, for example magnesium chloride; short chain 'monobasic carboxylicacids, for example formic acid, or the corresponding sodium or potassiumsalts, for example sodium acetate and sodium formate; fluorboric acidand its salts, for example sodium fluorborate; benzimidazoles, for example Z-methyl-benzimidazoles; aldchydes, for example paraformaldehyde;triazoles, for example 3-amino-l H- 1,2,4-triazole; piperazines, forexample 2-methylpiperazine; and acetylenic diols, for example2-butyne-1,4- diol. It is, of course, obvious that these are specificexamples that the general classes of compounds including carboxylicacids, fiuorboric acids, aldehydes, acetylenic diols, triazoles,benzimidazoles, piperazines, and related classes of compounds would tendto function to enhance, improve, and brighten coating to some extent.

Although I consider glutaric anhydride, sodium glycolate and succinicanhydride as my preferred enhancing and modifying agents, I haveexperimented with other agents including citric acid, gluconic acid,succinic acid, ethylenediamine tetracetic acid. These are only specificexamples, the series of related acids including tartaric, fumaric,maleic, propionic, butyric, valeric, and other similar acids areadaptable. I have discovered that, especially, glutaric anhydride,sodium glycolate and succinic anhydride, in combination with forexample, boric acid, citric acid or hydroxy acetic acid, impartsynergetic effects to the complexing and chelating agents employed,since the qualities of the plating are enhanced over those where any onemember of one group or one member of the other group are employed.

In the following examples of formulae, the preferred grade of boric acidis U.S.P.;- of glutaric anhydride, the the technical grade and sodiumglycolate, the purified grade. The sulfuric acid of the electrolyte ispreferably conventional 66 Baum in tap water, with the grades of thesalts of the plating metals those commonly used in immersionelectrolytic plating electrolytes.

Since very superior platings result from the use of boric acidassociated with glutaric anhydride in my formulations, the followingExample I is given.

EXAMPLE 1 Consisting of a dry admixture of the following composition tobe used in aqueous solution of suitable concentration to produce animmersion coating on steel objects, the percentages of specificingredients in this and the other examples are by weight, except asnoted herein- In place of glutaric anhydride, I may substitute sodiumride in an immersion plating bath consisting of boric acid, glycolate asfollows: nickel sulfate, copper sulfate, and stannous chloride modi-EXAMPLE 2 fies, enhances, and brightens the deposited coating. Thisconcept is illustrated in Example 5 in which the' ratios SpecificSpecific Dry 5 are merely specific examples of the genreal principle.Example, Admixture,

percent percent EXAMPLE 5 Boric acid 4. 38.1 Specific Specif c DrySodium glycolate 2.0 19. 0 Example, Admlxture, Copper sulfate 1. 0 9.Percent Percent Nickel sulfate 3. 0 8. 6 Stannous chloride (anhyd. 0.54.8 5.0 47.6 Sulfuric acid 0.5 1. 0 9. 5 Water 89. 0 1. 0 9, 5 3.0 28.6100. 0 100. 0 stannous chloride (anhyd.). 0.5 4i8 Sulfuric acid Water89.5 Instead of the glycolate or anhydride, I may substitute l5 citricacid, as follows: 100 0 0 EXAMPLE 3 The sodium chloride may be of anygrade from U.S.P.

XV to table salt. S ecific S ecific Dry Exgmpley Xdmixture, Threemod1ficat1ons of the foregoing formulae are percent percent contained inExamples 6 to 8. One illustrates the modification, improvement,enhancement, and brightening pro- Boric acid Citric acid... duced by theincorporatlon of succinic anhydride in an Copper sulfat Nickel sulfate.1mmers1on plating bath consisting of citric acid, copper,

nickel and stannous salts. The second and third are examples of themodification, improvement and enhancement resulting from theincorporation of either hydroxy acetic acid, or citric acid in animmersion plating bath consistin of Rochelle salts co er, nickel andstannou Or, in place of the above, I may substitute succmlc salm O pp Sacid, as follows:

stannous chlon EXAMPLE 4 EXAMPLE 6 ercent Percent percent Percent Boricacid. 0 1 Citric acid 5. 0 47. s Succimc ld- 0 0 Succinic anhydride- 1.0 9. 5 Copper sulfate. 1. 0 9. 5 Copper sulfatem. 1. 0 9. 5 Nickelsulfate.. 0 6 Nickel sulfate 3. o 28.6 st nnc ciflond y J- 5 8 Stannouschlorid 0. 5 4. s Sulfuric acid 5 Water 89. 5 Water 0 100.0 100 0 100 0m0 0 EXAMPLE 7 Alternatively, in place of succinic acid, I maysubstitute diglycolic acid, Rochelle salt, gluconic acid, salicylic Ella fl lg i ii ifi tr acid, ethylenediamine tetraacetate, or sodiumchloride. Percent: Percent As a reduction to practice Of the PI'O andPractice 11 1 11 11; 5,0 47, exemplified by the formulation containingboric acid C tr c acid 1.0 9.5 and glutaric anhydride, 100 millilitersof an eig -p i?5s%ii %f:: 3313:: $13 233 by weight solution of theelectrolyte of Example 1 was stannous chloride yd-L. 4:8 prepared. Mildsteel panels 20 gauge, 601d r ll 1 y Water 89'5 2 inches were coated byimmersion in this solution for 100.0 100.0 three minutes, after about 65panels had been coated, EXAMPLE 8 4 percent by weight of Example 1 wasadded to replenish the bath. The color and brightness of the Specific pi c coating was found to be excellent after 728 panels had i e ib iittififlf'ii iiiii been coated in 100 milliliters of this solution in thismanner. The solution was analyzed before use and after figf ifi ffiigggg -g $33 3:8 728 panels for boric acidby manitol titration, nickel byo p sulfate 1.0 9.3 dimethyl glyoxime, copper by thiosulfate titrationafter Nmkelsulfate ,12 11% 89.2

separation on aluminum foil, tin by precipitation from nitric acidsolution and iron by cupferron precipitation, 10m 1000 the stepsresulting in the following:

Additional examples in which succinic anhydride or Aft 728 P 1 BeforeUse, Percent er ,3 23 dlglYCOllC acid are employed are. Boric acid. 4.514. EXAMPLE 9 Specific S ecific Exampl Dry A zlmix- Percent ture, PercentlNeglielble- Born; acid 5.0 47.6 After 200 panels, the copper indicatedby titration was Q8 3:2 0.0095 and after 300 panesl, 0.025% expressed as1.2 9.5 metallic copper. Variations observed may be partly due 8: if tothe complexity of the analytical procedure. 100 0 100 0 It was observedthat the incorporation of sodium chlo- EXAMPLE 10 Specific SpecificExample, Dry Admir- Percent ture, Percent Boric acid 5. 47. 6 Diglycolieacid 1. 0 9. Nickel sulfate 3. 0 28. 6 Copper sulfate 1. 0 9. 5 Stannouschloride (anhyd 0. 5 4.8 Water 89. 5

as below:

EXAMPLE 1 1 Specific Specific Example, Dry Admix Percent ture, PercentSodium citrate 1. 5 25. 0 Versene 1. 0 16. 7 Copper sulfate 1. 0 16. 7Stannous chloride (anhyd 1. 0 16. 7 Sodium glycolate 0.5 8.2 Sodiumchloride 1. O 16. 7 Sulfuric acid (by volume) 0.5 Water 93. 5

Example 12 Specific Specific Example, Dry Admix- Percent turg, PercentAdherence of the plated coating was excellent at 8.4 and 10.0% iron.

A further binary metal plating formula is as follows, employing succinicacid:

Example 13 Specific Specific Example, Dry Admix- Percent ture, PercentBoric acid 5 50 Brightening agents were evaluated in the following bath:

Percent Boric acid 4 Citric acid 2 Nickel sulfate 3 Copper sulfate 1Stannous chloride (anhyd.) 0.5

The preferred concentration ranges in solution were:

Magnesium chloride 0.25 to 1.5%. Benzimidazole 0.05 to 0.5%.Z-methylbenzimidazole 0.05 to 0.5%. 2-methylpiperazine (70% soln.) 0.01to 0.25%. 2-butyne-1, 4- diol 0.1 to 0.25% or saturation.Paraformaldehyde 0.01 to 0.2% or saturation. 3-amino-1H-1,2,4-triazole0.01 to 0.25%. Sodium acetate 0.01 to 1% or saturation. Sodium formate0.01 to 1% or saturation. Sodium fluorborate 0.01 to 1% or saturation.

As an addition to the above generalized formulation, the optionalbrightening agent range may be 0.001 to 1%.

By the term complexing and chelating agent in the claims, is meant onethat exhibits chemical sequestering characteristics added to chelatingcharacteristics which affect the metal salts during plating. Enhancingand modifying agent is one that affects the complexing and chelatingagent so that the desirable results described in the fourth paragraph ofthis specification are achieved. By the term brightening agents is meantmaterials whose principal function in the plating bath seems to be toimprove the appearance of the deposited coating, by imparting luster orbrightness to the coating.

The actual steps in employing in immersion electroplating by the use ofthe new electrolytes of this invention are those generally used in theart.

In the above examples, the nickel sulfate is preferably the materialtermed hexahydrate (6H O) and the copper sulfate is preferably thematerial termed pentahydrate (SH O).

What is claimed is:

1. An immersion process for applying a brasslike liquor finish to steelwhich comprises immersing steel in an aqueous solution containing fromabout 0.01% to about 10% by Weight of a water soluble salt of copper,nickel, and tin, from about 0.5% to about 10% of a complexing agentwhich is a member of a group consisting of boric acid and citric acid,and from about 0.01% to ab ut 5% of an enhancing agent which is a memberof the group consisting of glutaric acid, succinic acid, and glycolicacid, their anhydrides and water soluble salts.

2. A process as in claim 1 where the complexing agent is boric acid andthe enhancing agent is glutaric anhydride.

3. A process as in claim 1 where the complexing agent is boric acid andthe enhancing agent is sodium glycolate.

4. A process as in claim 1 where the complexing agent is boric acid andthe enhancing agent is succinic acid.

5. A process as in claim 1 where the complexing agent is citric acid andthe enhancing agent is sodium glycolate.

6. A composition comprising a mixture of dry ingredients suitable foraddition to water to prepare an immersion coating solution for steelobjects comprising on a parts by weight basis from about 5% to about 10%of a water soluble copper salt, from about 25 to about 30% of a Watersoluble nickel salt, from about 3% to about 5% of a water soluble tinsalt, from about 25% to about 50Z of a complexing agent selected from agroup of boric and citric acids, and from about 10% to about 25% of anenhancing agent selected from a group consisting of the free acid, itssalt, or the anhydride of glutaric, succinic, and glycolic acids. 1

7. A composition as in claim 6 where the complexing agent is boric acidand the enhancing agent is glutaric anhydride.

7 8 8. A composition as in claim 6 where the complexing 3,032,486 /1962821110 et a1 20443 agent is boric acid and the enhancing agent is sodiumgly- 3,149,057 9/1964 Parker et a1 204-43 XR colatc. 3,149,058 9/ 1964Parker et a1 204-43 XR 9. A composition as in claim 6 where thecomplexing 3,211,578 1965 Gutzeit 106-1 agent is boris acid and theenhancing agent is succinic 5 3,380,898 4/1968 Danemark et a1. 20444acid.

10. A composition as in claim 6 where the complexing FOREIGN PATENTSagent is citric acid and the enhancing agent is sodium gly- 1,162,3989/1953 France 601m 871,276 6/1961 Great Britain.

References Great UNITED STATES PATENTS OTHER REFERENCES 570,554 11/1896Jordis 204-44 IBMT h 1 D 1 B 11 1 4 N 2,081,630 5/1937 Leonard 1O6 1 XRApril 19;; me we osure u e 1n, vo o. 11, p. 10, 3,346,404 10/1967Gardner et a1. 1061 1,837,835 12/1931 Pinner et a1. 20443-XR JOHN MACKPrimary Examiner 2,411,674 11/1946 Wilson 20452 437 355 3 1943 Stareck204 52 KAPLAN, Asslstallt EXamlIlel' 2,653,128 9/1953 Brenner et a1.20443 U S Cl X R 2,773,818 12/1956 Moy et a1 Z0449 2,882,208 4/ 1959Becking et a1 20449 117130; 20444,

